Low-Power Wideband Analog Channelization Filter Bank Using Passive Polyphase-FFT Techniques

Abstract

Polyphase-FFT (P-FFT) techniques allow for low power implementations of high performance multi-channel filter banks by utilizing computation sharing like a standard fast Fourier transform (FFT). Additionally, it enables a longer “effective window length” than is possible in a standard FFT. This characteristic breaks the trade-off between the main-lobe width and the side-lobe amplitudes in normal finite impulse response filters. Thus, P-FFT techniques have been employed for the channelization of wideband input signals in high speed digital communication receivers. In this paper, we present a prototype analog P-FFT based filter bank in discrete time that is used to channelize wideband input signals so as to reduce the speed and dynamic range requirement of the ADCs. The four-channel I/Q prototype is implemented using TSMC’s 65 nm GP technology. Based on passive switches, the design operates at high speed, consumes low power, and offers high linearity performance. The measured transfer function shows >38 dB side-lobe suppression at 1 GS/s operation. The average measured IIP3 is +25 dBm differential power and the total integrated output noise is 208 $\mu V_{\mathrm{ rms}}$ . The total power consumption for the P-FFT filter bank (eight-channels total) is 34.6 mW (34.6 pJ/conv).